This invention relates generally to improvements in irrigation control systems particularly of the type for automatic supply of irrigation water to sprinklers at preselected start times and for watering cycles of programmed duration. More specifically, this invention relates to a relatively simple rain detection device for preventing or halting supply of irrigation water to sprinklers in the presence of a predetermined amount of rainfall.
Automatic irrigation control systems in general are well known and commonly include a preprogrammed timer or clock controller for electrically operating a plurality of sprinkler valves, each of which in turn controls supply of irrigation water to one or more irrigation sprinklers. Each sprinkler valve typically includes an electrically operated valve actuator, such as a solenoid actuator, which is normally closed to prevent supply of irrigation water to its associated sprinklers. However, upon receipt of an appropriate actuation signal from the clock controller, the valve actuator is displaced to an open position, thereby initiating water supply to the associated sprinklers in accordance with controller-programmed start times and watering cycle durations. Such automatic irrigation control systems are highly advantageous in that watering cycles can be started and stopped without operator attention. Moreover, such automatic systems insure regular supply of irrigation water in accurate quantities without risk of overwatering and attendant water waste.
Automatic irrigation control systems of the type described, however, are designed to continue programmed watering cycles, irrespective of natural rainfall. Accordingly, such control systems may supply irrigation water to vegetation during or immediately subsequent to a substantial rainfall, resulting in water waste and potentially harmful overwatering of the vegetation. In existing automatic control systems, to prevent continued operation when a significant rainfall has occurred, it has been necessary to manually interrupt the control system, for example, by interrupting timer components for the controller. Such manual interruption, of course, requires operator presence and operator attention and further requires subsequent manual resetting of the system for resumed operation when desired.
There exists, therefore, a significant need for an improved automatic irrigation control system including means for automatically interrupting system operation upon detection of significant rainfall and for automatically resuming system operation at a later time in accordance with the amount of rainfall received. The present invention fulfills these needs and provides further related advantages.